RULE #1 OF ANY COLLECTIBLE CARD GAME: ONLY SPEND WHAT YOU CAN LOGICALLY AFFORD.
My weakness for Magic the Gathering was not wholly but partly responsible for some rough financial straits I found myself in from about 1995 to 1997. I still have about 10,000 cards or so to prove it. It's like cigarettes, but without the nicotine and smoke. First, you buy just one pack, "because it's only a few dollars." Then, you start buying entire boxes of 36 packs at a time, "just to build up a trading stock." Next thing you know, you're buying several boxes at once, "Because you just GOTTA have four Shivan Dragons to make your next deck concept work."
My name is Henry Link, and I am a Magic Addict. I've been clean for 2 years, 3 months, and 4 days now - But I NEVER forget where I've come from.
UNLIKE addiction, I can still occasionally play a casual friendly game, and I keep about 20 complete decks on hand for this purpose. However, I have long ago since learned to find out NO NEW INFORMATION about new expansions, because all it would take is one new cool ability, one cool deck concept, and I'm back off the wagon.
Magic the Gathering is one of the most fun games I've ever played, because of the permutations available, and the new deck strategies people come up with in a limited environment.
My advice? No more than one starter deck and a few boosters per player, and see what neat ideas you can all come up with, using just the limited pool of cards. If one person has a highly customized deck, it starts a buying escalation with all the other players. Be careful not to get into that situation, because before you know it you'll have far mroe than you can possibly use.
But it's incredible fun.